Multiscale Simulations of Hydrochlorination on Si and Cu3si Surfaces with Applications for Polysilicon Production

摘要: Surface reactions of the chlorosilane based chemical systems present during hydrochlorintaion or chemical vapor deposition in the Siemens process for solar grade silicon production have not been extensively explored and there are few ab-initio simulations for them. We conducted density functional theory simulations to establish reaction networks involving 14 species on a Si (100) surface (27 elementary processes) and catalytic Cu3Si surface (20 elementary processes). These involved adsorption, removal of Si atoms from solid surface, surface intermediate formation, diffusion and gas product desorption. The production of trichlorosilane (SiHCl3, TCS) had four different possible reaction pathways. The resulting elementary processes were then simulated using kinetic Monte Carlo over a temperature range of 700-1200 K. The turnover frequency (TOF) of TCS production on the Cu3Si surface was at least four orders of magnitude higher over the entire temperature. The SiCl2* and SiH2Cl* intermediates were found to be important for the Si surface, while SiCl2* and SiCl3* were most important for the Cu3Si surface. The Cu3Si surface had higher selectivity for TCS production than the Si surface for most of the temperature range. The maximum production rate and selectivity for TCS was found on the Cu3Si surface at 950 K.